Dong Kang, Markötter Henning, Sun Fu, Hilger André, Kardjilov Nikolay, Banhart John, Manke Ingo
Institute of Materials Science and Technology, Technical University Berlin, Hardenbergstraße 36, 10623, Berlin, Germany.
Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109, Berlin, Germany.
ChemSusChem. 2019 Jan 10;12(1):261-269. doi: 10.1002/cssc.201801969. Epub 2018 Oct 31.
The internal microstructure of a silicon electrode in a lithium ion battery was visualized by operando synchrotron X-ray radioscopy during battery cycling. The silicon particles were found to change their sizes upon lithiation and delithiation and the changes could be quantified. It was found that volume change of a particle is related to its initial size and is also largely determined by the changing surrounding electron-conductive network and internal interface chemical environment (e.g., electrolyte migration, solid-electrolyte interphase propagation) within fractured particles. Moreover, an expansion prolongation phenomenon was discovered whereby some particles continue expanding even after switching the battery current direction and shrinkage would be expected, which is explained by assuming different expansion characteristics of particle cores and outer regions. The study provides new basic insights into processes inside Si particles during lithiation and delithiation and also demonstrates the unique possibilities of operando synchrotron X-ray imaging for studying degradation mechanisms in battery materials.
在电池循环过程中，通过原位同步加速器X射线成像技术对锂离子电池中硅电极的内部微观结构进行了可视化观察。研究发现，硅颗粒在锂化和脱锂过程中尺寸会发生变化，且这些变化可以被量化。结果表明，颗粒的体积变化与其初始尺寸有关，并且很大程度上还取决于颗粒内部电子传导网络的变化以及破碎颗粒内部界面化学环境的变化（例如电解质迁移、固体电解质界面扩展）。此外，还发现了一种膨胀延长现象，即即使在改变电池电流方向并预期会发生收缩之后，一些颗粒仍会继续膨胀，这可以通过假设颗粒核心和外层区域具有不同的膨胀特性来解释。该研究为锂化和脱锂过程中硅颗粒内部的过程提供了新的基础见解，同时也展示了原位同步加速器X射线成像在研究电池材料降解机制方面的独特可能性。
